Rubber coated article



June 14, 1938. E C. DQMM 2,120,738

RUBBER COATED ARTICLE I Original Filed Feb. 10, 1936 Patented June 14, 1938 RUBBER COATED ARTICLE Elgin carleton Damm, Niles, Mieli., miami to National-Standard Company, Niles, Mich., a corporation of Michigan original application February 1o. 1936, serial No.

63,254.' Divided and this application June 16 1937, serial No. 148,621

Claims.

This invention relates to a method of applying a molten coating of metal over another coating of metal normally adversely affected by such a molten coating, and to the objects so produced.

In the production of metal objects it is frequently desirable to apply a second coat over an inner one. Ordinarily the second coat will be of the same metal as the lower one, but this is not always the case. The most economical method at present is to coat with a molten metal, but where this is attempted, dipping the coated base into the molten body dissolves most or all of the lower coating, and it is thus not practicable to build up a thick coat in this manner.

For example, it is frequently desired to increase the corrosion resistance of ferrous base objects by the use ofv zinc. But attempts to apply more than one coat of zinc by the hot dipping process failed to increase ,the thickness materially.

In accordance with the present invention a thin layer of an inert metal is deposited on the first coating, then the object may be coated with molten metal without affecting the lower layer. This is illustrated diagrammatically in the drawing in which Fig. 1 represents diagrammatically a section broken away through a coated base and Fig. 2 represents a similar view through another base provided with additional coatings. The base is shown provided with a layer of relatively low melt point metal on which is a thin layer of relatively high melt point metal followed by a hot dipped coating of a relatively low melt point metal.

The layer of relatively high melt point metal, which may be designated as a flash, is applied by any method not adversely affecting the lower coat. Such methods may be designated as cold methods, even though they may involve the use of considerable heat, and even though in some instances the metal may be applied in molten or gaseous state, as for example in the sputter processes. Ordinarily, of course, the coating will be applied by electroplating, which Will include dep-` osition by substitution. 'I'he substitution method is not preferred because it uses up some of the lower coating of metal.

The thickness of the coating is such that from a heat capacity standpoint it has a negligible insulating effect Why such a thin coating should insulate the metal beneath is not known. It is possible that the metal maintains a shell which prevents the lower material from running off even though melted and even though the shell may not be entirely continuous.

Surprisingly enough, the coating of inert metal-which is ordinarily a high melt point metalis effective even though it is almost immeasurably thin. As a result the amount of the inert metal is so little that it does not adversely aifect corrosion resistance or other properties of thek composite object.

For example, a ferrous base, such as a tire bead reenforcing wire having a diameter oi' .037 inch may be dipped in molten zinc to apply a galvanized zinc coating. Such a coating is ordinarily about 0.00017 inch in thickness, or contains about 10 grams of zinc per kilogram of wire. An electroplating of copper is then put upon the galvanized wire to the amount of about 12 grams of copper per kilogram of' wire. 'I'hls coat is thus of the order of 0.0001 inch in thickness. The wire may then be again immersed in zinc. and a second coating of about 10 grams per kilogram applied thereon, without affecting the rst coating. In this case, the copper apparently produced an lntermediate area of brass during the immersion.

The invention is particularly applicable to the production of multiple coats by the hot dipping process, and is applicable to coating with any metal by the hot-dip process upon any other thin coating of metal which ordinarily is adversely affected by the hot dip.

The invention is applicable to a very large number of combinations of metals, primarily being used where it is desired to put a coating of metal by the hot-dip process upon another metal having a similar or lower melting point. However, in many instances it is impossible to plate by the hot-dip process a metal of relatively low melt point upon a metal which has a considerably higher melting point due to the formation of undesirable products. For instance, cadmium cannot be plated upon zinc in the ordinary hot method due to the formation of a watery alloy, even Y though the melting point of cadmium is very considerably below that of zinc.

The following table shows a number of examples of the process:

Inner coating Intggga Outer coating Copper Hot cadmium. I Antimony Hot cadmium. N1ckel Hot cadmium.

Hot zinc-antimony Hot lead. Lead-arsenic (hot or cold) Hot lead. Heavy electro-zinc Hot cadmium. Hot zinc-Electi-o-zinc. Hot cadmium. Hot lead-Electro-lead Copper Hot lead.

In all of the above cases, the original coat consisted of about 10 grams per kilogram of wire of .037 to .093 inch diameter, the intermediate coat of copper per kilogram of wire.

gram per kilogram, and the outer coat was approximately 10 grams per kilogram. For other diameter wires coatings of similar thickness are employed. Other metals such as antimony, chromium, silver, and the like may be used as an intermediate coating, the amounts required varying for the various metals. Antimony, for example, may require about 12 grams per kilogram, owing to its low melting point. In the case of readily oxidizable metals, care should be taken to avoid oxides in order that subsequent coats may adhere.

The process affords a very desirable method of putting tin upon an object. For example, copper was applied at the rate of .02 ounce per square foot over a hot tinned brass strip, and additional hot tin was then applied over the copper.

As another example of the invention a hot galvanized wire bead reenforcing wire having a coating of approximately 11 grams of zinc perkilogram of wire was electroplated with .25 gram An outer coat of cadmium was then applied by the hot-dip process, the temperature of the cadmium bath being about degrees higher than the melting point of the cadmium. By this means about 10 to 11 grams of cadmium per kilogram of wire was applied.

In case of tire bead reenforcing wires the wire may be coated with zinc, then with copper, then with zinc, and again with a coat of copper to which rubber is vulcanized. In such a case the second layer of copper is of the order of 0.00001 of an inch, and by alloying with the zinc becomes rubber adherent. The rst coating of copper may be of the order of .0001 inch in thickness.

As a further example of the invention, a ferrous tire bead having a diameter of .037" or other ferrous base object may be galvanized with zinc, electroplated with a flash of nickel, and then a hot-dipped layer of cadmium applied to the nickel, followed by a thin layer of antimony or arsenic on the cadmium. A wire so coated has extremely high corrosion resistance, particularly to corrosion of the type of which the salt spray is typical.

'Ihe thickness of the galvanized zinc coating will ordinarily be sucient to provide about 10 gm. of zinc per kg. of wire. Considerably thicker coatings, however, will not adversely aifect the product. Nickel may then be electroplated to the amount of .1 to 1.5 gm. of nickel per kg. of wire, and the wire is then admixed in molten cadmium which will apply a coating of about 10 gm. per kg. of wire, and will not adversely affect a lower coating of zinc. It is preferred to wipe all hotdipped coatings.

Antimony may then be applied to the cadmium from an electrolytic solution of the metal, such as is described in myco-pending application Serial No. 32,298, filed July 19, 1935.

It may be prepared, for example, by dissolving 3 oz. of sodium cyanide in 1 gallon of Warm water, dissolving 1A oz. of antimony trisuliide in the solution, and then heating to F. 'I'he solution is preferably maintained at about this temperature during the reaction. The coated material is then immersed in the bath for a short period, normally long enough to produce a coating of the orderof 0.1 gram to .35 gram of antimony per kilogram of wire. Normally, an immersion of 3 to 10 seconds is suilcient. 'Ihe coating of antimony will be of the order of .005 oz. of antimony per square foot of surface. The article is prefer- .was electroplated and was of the order of .4 to .8

ably washed in cold water and then carried while still wet to a bath of boiling water, and is then air-dried while still hot, the air-drying taking place rapidly enough to prevent corrosion.

The antimony not only increases the corrosion resistance of the material to which it is applied, but when plated in a thin layer, is particularly valuable in connection with articles which are to be vulcanized to rubber, inasmuch as it apparently alloys itself with the cadmium in such a manner as to produce a rubber-adherent material. y

In the case of the zinc-nickel-lead coating heretofore described, the zinc coating may be hot dipped, followed by. electroplating. The` coating may also be entirely electroplated, if desired. Its thickness may vary from .0001 inch upward, but normally will not exceed .004 inch. The weight -per unit area of zinc will thus be approximately either by the hot dip process, or by the electrolytic process, or by the hot dip process followed by electroplating. The thickness of the lead will vary from about l/ 15,000 to 1/ 1000 of an inch or, expressed in weight per unit area, from about .25 to 3.75 grams per square foot of Vsurface covered.

An iron base so coated with zinc, nickel and lead has extremely high corrosion resistance, particularly in acid atmospheres.

It will be appreciated that the flash coating of high melt point metal interposed between the two hot-dipped coats may, in general, so alloy itself with one or both of the coats, that it loses its identity as an individual layer. The claims therefore must be interpreted from the standpoirt of the time of application of the various coa s.

This application is a division of my co-pending application Ser. No. 63,254 filed February 10, 1936, which was a continuation in part of application Sez'. No. 749,303 filed October 20, 1934, and of application Ser. No. 30,919 filed July l1, 1935.

What I claim as new and desire to secure by Letters Patent is:

1. A metal coated object comprising a base, a coating of zinc thereon, an intermediate ash coating thereon of a relatively high melt point metal, and a hot-dipped outer coating of cadmium o n the intermediate coating.

2. An object as set forth in claim 1, in which the coating of zinc is hot-dipped.

3. An object as set forth in claim l, in which the intermediate coating isy of nickel.

4. A ferrous base wire having a hot-dipped layer of zinc thereon, a flash layer of a relatively high melt point metal thereon, and an outer hotdipped coating of cadmium thereon.

5. A metal-coated object comprising a ferrous base, a hot-dipped zinc coating thereon, a flash coating of a relatively high melt point metal on the zinc, a hot-dipped coating of cadmium thereon, and a thin layer of antimony on the cad- 6. An article as set forth in claim 5, in which the antimony has a thickness of the order of .005 oz. per square foot of area.

` '7. An article as set forth in claim 5, in which the intermediate high melt point metal is nickel.

8. A metal-coated object comprising a ferrous base, a hot-dipped zinc coating thereon, a ash coating of a relatively high melt point metal on the zinc, a hot-dipped coating of cadmium thereon, a thin layer of antimony on the cadmium, the antimony being thin enough to alloy throughout with the cadmium at atmospheric temperature or the temperature of vulcanization, and a layer of rubber vulcanized thereto.

9. A tire bead reinforcing wire comprising a ferrous base wire, a hot-dipped zinc coating thereon, a ash coating of nickel on the zinc, a hot-dipped coating of cadmium on the nickel, and

a thin layer of antimony on the cadmium, the antimony being thin enough to alloy throughout with the cadmium at atmospheric temperature or the temperature of vulcanization.

10. In a tire bead, a ferrous base tire bead wire having a hot-dipped zinc coating thereon, a flash coating of nickel on the zinc, a hot-dipped coating of cadmium on the nickel, a thin layer of antimony on the cadmium, the antimony being thin enough to alloy throughout with the cadmium at atmospheric temperature or the temperature of vulcanization, and rubber vulcanized thereto to y produce a tire bead.

` ELGIN CARLETON DOMM. 

